The long-term goal of this research program is to understand the impact of early-life affiliative experiences on social behavior in a bi-parental mammal. We will examine the developmental consequences on neurobiology and behavior resulting from 'broken homes' in which fathers are absent, or mothers compromise offspring care for food acquisition. Parent-offspring interactions provide the principle social experiences for developing young, and may have life-long ramifications that shape social decisions. Humans are bi-parental. Unfortunately, most of what we know about behavioral development comes from species whose social organization differs significantly from our own. The hormones oxytocin (OT) and vasopressin (VP) are inextricably linked with the control of social behavior and are particularly well known for their influences on parental care and affiliation. Our recent work has demonstrated that fathers impact offspring adult social interactions, and the postnatal environment shapes OT and VP receptor expression in the developing brain. Thus, the ontogenetic changes in social behavior are probably rooted in concurrent changes in the social brain. Our hypothesis is: manipulating bi-parental care will produce offspring with varied social and cognitive ability, which will relate to physiological differences in oxytocinergic and vasopressinergic gene expression. The substantial knowledge about prairie vole social behavior (including bi-parental care) and neurobiology (OT and VP systems in particular) makes these socially monogamous animals an exceptional model to test this hypothesis. Our general approach is to determine if the presence or absence of caregivers in the postnatal environment influences cognitive development or social behavior, and determine if developmental differences in OT or VP relate to behavioral outcomes. In Aim 1, we will contrast paternal and maternal care to identify consequences of pre-wean social experience, by either reducing paternal care (removing fathers) or increasing maternal care (inducing licking / grooming). We will determine the importance of fathers on offspring development and if mothers compensate for absent fathers. In Aim 2, we will investigate the influence of 'single working moms' on offspring. By increasing the difficulty for access to food, mothers will be faced with the inherent trade-off between working for food or caring for offspring. In both aims, we will evaluate offspring social anxiety, social cognition, exploration, aggression, and social preferences, and we will characterize the expression of OT, VP and their receptors. These studies will provide a clearer picture of the importance of bi-parental care. This proposal significantly advances the NIH mission to pursue 'fundamental knowledge about the behavior of living systems' and is designed to improve both mental health and health in the process of human development. This work will reveal much of the neurobiology that underlies postnatal development, and could foster a deeper understanding of mechanisms regulating human social behavior and dysfunction.